Rock drill



W.' A. SMITH.

I ROCK DRILL.

APPLICATION man Aue.13, I920.

1,418,333. v Patented June 6, 1922.

ENTOR ATTOFiNEY its. sons,

. WILLIAM-5A. SMITH, or rHILLrPsBUI-te, NEVJJERSEY, AssreNoaTo IneEnsoLL- RAND, COMPANY, or JERSEY CITY, new JERSEY, a CORPORATIOII or NEW JERSEY.

ROCK DRILL.

Specificationof Letters Patent. Patented J .6 1922:

ApplicationfileclAugust 13, 1920. Serial no. 403,356.

a second head of smaller diameter connected with the main head by a reduced neck.

. Means are provided for maintaining con stant pressure behind the main headfor driving the piston forwardly, and in such case pressure is intermittently supplied to and exhausted from the-main bore of the cylinder in front of the main head, and supplied to and exhausted from the smaller bore of the cylinder behind the headofsmaller diameter.

The primary objects of the invention are to lengthen the backtravel of the piston and also produce a longer admission of fluid pressure against the rear forwardly driving pressure surface of'the head of smaller diameter on the'forward stroke. This is accomplished by producing a late admission against-the said'r'ear surface ofthe smaller head-on the rearward stroke anda late out off on'the forward stroke; I'prefer to provide a valve for carrying out the-purposes of the invention controlling communication between forward and rearward admission passages leading respectively to a forward admission port and another admission port located rearward of said forward admission 1 tends in position to receive the impact blows of'the piston hammer, which comprises the main piston head D and the head of smaller diameter connected to the main'head by means of the reduced neck '13. The piston may also be provided with the forwardly extending reduced shank G if desired.

' The main piston head D reciprocates within the larger bore H of the cylinder and in this instance the smaller head E reciprocates in a portion ofthe cylinder having a boreJ of smaller diameter and the back head K is bored to the same diameter to receive the head E inits travel. The main cylinder bore H is provided with a main exhaust port Land the backhead is provided with the exhaust p'ort 0 both con trolled directly by the piston. Pressure is constantlyrmaintained on the forwardly act'- ing pressure surfacewor shoulder P of the main'head D from the inlet Q and the fluid pressure-is distributed'to the ends of the cylinder by .suitable ports and passages partly controlled by the piston andpartlycontrolled by a valve.-

The supply of fluid pressure to t-he front end of the cylinder in front of the main head D passes through the supply port R and passage S directly to the admission port T,.the port B being controlled directly by the piston in its travel. The supply offiuid pressure to'the rear end of the smaller bore of the cylinder behindthe smaller: head E is'partly controlled by the valve U, in this instance shown provided with theforward headV,the-central head W and therear head- X, [connected by the necks. V. andwX. The valve-is subject to fluctuating pressure on two of its opposed-operative surfaces, in this instance the forward surface: Y of the forward head V beingsnbjected to the fluctuating pressure in the supply passage S communicating with the? front. end-of the cylinder, and therear surface Z of the rear head X is subjectto thefluctnating pressure in the passages to and 6 leading tothe'rear endof theusmaller bore of the cylinder: in tllBwbZlCk he'adxK. A forwardfadmission port 0 has a forwardadmissionpassage d leading to the valve chambers and the rearwardjadmission port f hasea rearward admission passage g leading to the valve chamber 6, both forward and rearward admission ports 0 and f communicate with the smaller bore of the cylinder. The front end of the valve chamber 6 as shown is provided with an atmospheric port it controlled by the front valve head V and an anti-compression port j for the front end of the main cylinder bore located forwardly of the supply port R and exhaust port L communicates with the valve chamberby means of the passage 76, and is opened to the atmosphere when the valve is in the position of Figure 2.

In the operation of themachine, let it be assumed that the piston is at the forward end of its stroke and is about to start on the back stroke as indicated in Figure 1. The exhaust port 0 at the back end of'the smaller bore of the cylinder is open and pressure is also exhausted from the rear pressure surface Zofthe valve U through the passages a and 'b to the rear end of the cylinder and thence to atmosphere, The live pressure on the front surface Y of the valve head V has caused the valve to throwover or move to its rearward position as indicated in Figure 1, closing communication between the forward and rearward admission passages (Z and 9.

As the piston travels back, the exhaust port 0 for the rear of the smallerbore, and the supply port R for the forward end of the larger bore, are closed, but the shoulder 0 at the neck of the piston overruns the for ward admission port 0, without admitting pressure to the rear surface ;0 of the smaller head E, because the forward admission passage d is still closed by the valve U.

I After the main head D over-runs the cylinder exhaust port L, the exhaust from'the forward end of the cylinder is opened, which also opens the front end Y of the valve U to exhaust through the passage S and front end of the cylinder and exhaust port L. The shoulder 0 on the neck of .the piston then over-runs the rearward admission port 7, which admits pressure past the piston neck F to the rear of the smaller head E of the piston, and also through the passage a to the rear end'Z of the valve U, which throws the valve to its forward position as indicated in Figure 2, thus opening communication between forward and rearward admission passages d and g, and supplying full pressure behind the smaller piston head E for the forward stroke.

Owing to the fact that no'pressure is supplied to the rear of the smaller cylinder bore behind the smaller head E when the forward admission port 0 is uncovered by the piston shoulder "0, the piston has a substantially long rearward stroke, before the forward and rearward admissionpassages d and g are placed in communication by the action of the valve U and on the other hand, the piston is'given a late cut-off on the forward stroke, because cutoff does not take place I piston as indicated in Figure 1.

The communication between the anticompression port j and the atmosphere is closed by the valve head V when the valve is in the position shown in Figure 1, but the'anticompression port is open to atmosphere when the valve is in the position in Figure 2, and the piston is on its forward stroke. The anti-compression port remains open after the main exhaust port L is closed by the: piston and relieves compression in the forward end of the cylinder. a c

I claim: V 1

1. In a fluid operated rock drill of the hammer type, the combination of a cylinder and a differential piston constructed with a main head and a rear head of different diam- Y by the main piston head and communicating I directly with an admission port at the forward end of thecylinder for supplying motive fluid to the rearwardly acting pressure surface, a piston controlled exhaust port for the cylinder, an anticompression port for the forward end of the cylinder located forwardly of said supply and exhaust ports, a forward admission port and another admission port rearward of said forward admission port for supplying motive fluid to the other of said forwardly actingpressure surfaces of the piston, and a fluid actuated valve for controlling communication between forward and rearward admission passages leading to said forward and rearward admission ports and for controlling communication between said anti-compression por and the atmosphere. y

2. In a fluid operated rock drill of the hammer type, the combination of a cylinder and a differential piston constructed with a main head anda rear head of different diameters connected by a reduced neck and having two forwardly acting pressure surfaces and a rearwardly acting pressure sur-.

face, means for constantly supplying fluid pressure toone of said forwardlyyacting pressure surfaces, a supply port controlled directly by the main piston head and communicating directly with an admission port at the fo rwardend of the cylinder for supplying motive fluid to the rearwar-dly acting pressure surface, a piston controlled exhaust port for the cylinder, an anti-compression port for the forward end of the cylinder located forwardly ofsaid supply and exhaust ports, a forward admission port and another admission port rearward'of said forward adadmission passages leading to said forward mission port for supplying motive fluid to and rearward admission ports and for conthe other of said forwardly acting pressure trolling communication between said antil0 surfaces of the piston, and a fluid actuated compression port and theatmosphere.

5 Valve subject to fluctuating pressure on op- In testimony whereof I have signed this posed operative surfaces for controlling comspecification. munication between forward and rearward WILLIAM A. SMITH. 

